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Old 26th June 2023, 00:34   #1  |  Link
kurkosdr
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Is HDR10 possible in broadcast?

Basically as the title says:

Is HDR10 possible in broadcast? By broadcast I mean DVB-T2, DVB-S2, ATSC 3.0 etc

The reason I am asking is because all the broadcast HDR channels I see are HLG, and also in HDR10 you need to know the average light level and maximum light level in advance, which I am not sure it can be done in a broadcast channel where you have a single uninterrupted stream that can have all kinds of content coming back-to-back.

So, asking if it's even technically possible, aka if it's technically possible we'll get some boutique HDR10 channel on satellite or cable someday.

Last edited by kurkosdr; 26th June 2023 at 17:28.
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Old 26th June 2023, 16:37   #2  |  Link
FranceBB
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Short answer:

Yes, it's possible.
No, it won't happen anytime soon.

Long answer:

I did a demo for Samsung a few years ago with algia here in the forum (Livio Aloja), now retired.
It is possible to air HDR PQ contents via satellite and in my test I demonstrated how bringing everything to 1000 nits PQ the results were consistent with what we expected.
The issue is that we can't have dynamically changing metadata, therefore, although everything could be aired in PQ, you would have no way of telling the decoders that, let's say, a movie is 1200 nits and a commercial is 385 nits.
Everything has to be consistent and everything has to be at the same MaxCLL.
So, forget HDR10+ and forget Dolby Vision, but as long as everything stays the same, it's gonna be fine.
Now, since you pay the bandwidth like gold on hotbird (which is ridiculously old and overcrowded), airing in PQ would cut off a big chunk of viewers, which is why everyone airs HLG.
With HLG you can serve both those whose set can understand the transfer characteristics (arib-std-b67) and have an HDR TV and those who have a UHD BT2020 SDR 100 nits TV as they will take the same signal, ignore the transfer characteristics and display it as is.
The only "issue" will be that the reference white will peak at 0.52V (namely 75%, so 75 nits) rather than 0.7V (namely 100%, so 100 nits) in those BT2020 SDR TVs, but still that's considered acceptable, while such a thing couldn't be done for PQ as it's a completely logarithmic curve whose blacks start much higher and whose whites peak much lower.
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Old 26th June 2023, 17:51   #3  |  Link
kurkosdr
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Quote:
Originally Posted by FranceBB View Post
Short answer:

Yes, it's possible.
No, it won't happen anytime soon.

Long answer:

I did a demo for Samsung a few years ago with algia here in the forum (Livio Aloja), now retired.
It is possible to air HDR PQ contents via satellite and in my test I demonstrated how bringing everything to 1000 nits PQ the results were consistent with what we expected.
The issue is that we can't have dynamically changing metadata, therefore, although everything could be aired in PQ, you would have no way of telling the decoders that, let's say, a movie is 1200 nits and a commercial is 385 nits.
Everything has to be consistent and everything has to be at the same MaxCLL.
So, forget HDR10+ and forget Dolby Vision, but as long as everything stays the same, it's gonna be fine.
Now, since you pay the bandwidth like gold on hotbird (which is ridiculously old and overcrowded), airing in PQ would cut off a big chunk of viewers, which is why everyone airs HLG.
With HLG you can serve both those whose set can understand the transfer characteristics (arib-std-b67) and have an HDR TV and those who have a UHD BT2020 SDR 100 nits TV as they will take the same signal, ignore the transfer characteristics and display it as is.
The only "issue" will be that the reference white will peak at 0.52V (namely 75%, so 75 nits) rather than 0.7V (namely 100%, so 100 nits) in those BT2020 SDR TVs, but still that's considered acceptable, while such a thing couldn't be done for PQ as it's a completely logarithmic curve whose blacks start much higher and whose whites peak much lower.
Glad to know it can at least be done, if I understand correctly, you are "stretching" or "companding" the levels of each content to 1000nits in order to have a consistent average and maximum light level. Nice.

About the other thing, aren't most "UHD" TVs supposed to support HDR10? There were some early 4K TVs that were SDR, but not many were sold and even fewer of them support 10-bit HEVC decoding. And HD TVs don't support HEVC (much less 10-bit 4K HEVC) anyway.

Or the problem is that HDR10 cannot be converted by a set-top box to SDR? Can a set-top box convert HDR10 -> SDR?

(also, some broadcasters are leaving Hotbird, precisely because they are finding less and less value in cramming themselves in crowded Hotbird when there are other satellites available)

Last edited by kurkosdr; 26th June 2023 at 17:56.
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Old 26th June 2023, 18:09   #4  |  Link
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Quote:
Originally Posted by kurkosdr View Post
Or the problem is that HDR10 cannot be converted by a set-top box to SDR?
It's not a matter of what a set top box can do but rather what it's allowed to do.
Over the last few years, many content providers allowed the automatic conversion from BT2020 HLG to BT709 SDR done on the set top box end. Not all of them, but most of them.

None of them however accepted this for BT2020 PQ to BT709 SDR.
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Old 26th June 2023, 20:46   #5  |  Link
kurkosdr
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None of them however accepted this for BT2020 PQ to BT709 SDR.
Oh, I see. Do you have any public information about this (links)? It's OK if you don't, just asking.

BTW when it comes to free-to-air terrestrial broadcasting, I do find it dumb to bend over backwards to serve HDTVs, since most people won't buy a set-top box anyway (anyone who cares about receiving UHD channels will simply buy a new TV supporting UHD - including HDR). I mean, some countries still broadcast the majority of their channels in MPEG2 SD precisely because people are so reluctant to buy set-top boxes for free-to-air terrestrial.

But when it comes to sat and cable, I understand why. Broadcasters want to have one stream and ship one set-top box and have it work on all TVs (HD and UHD).
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Old 27th June 2023, 22:50   #6  |  Link
benwaggoner
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ATSC 3.0 absolutely supports HDR-10 PQ + Rec. 2020 as a specification. And since both DoVi Profile 8.1 and HDR10+ dynamic metadata are carried in the elementary s team, as long as the decoder can extract the SEI/NAL unit data and pass it off to the system for use in on-device tone mapper or HDMI output, the dynamic metadata can be used. This has been the Dolby Vision Plan A for live HDR all along.

The "backwards compatibility over fixed RF-bound bandwidth" is the big challenge, and it's why live HDR-10 has mainly been seen in IP delivery. Separate Native SDR and Native HDR-10 provide a better experience than HLG, and if you can target the right stream to the right device, have broader HDR compatibility.

HLG is something that "works in practice, but not in theory" - it's just not possible to encode two distinct creative intents using identical code values without metadata. HLG + dynamic metadata (which is how Apple's HDR video recording works) could do a lot better, but I don't know that anyone has even considered it for broadcast or streaming.
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